group 2 elements(alkali earth metals)

• What are the solubility rules?

  - Ca(OH)₂ and CaSO₄ sparingly soluable with  BaSO₄ insoluable.

  -In hydroxides,up the group solubility increases.In the sulfates solubility increases down the group.
• What is Ca(OH)2 used for?

  'Slaked lime'-used to treat acidity in soil where crops grow as they need a PH closer to neutral to grow properly.
• What is Mg(OH)2 used for?

  'Milk of magnesia'-treats indigestion by removing excessive stomach acid.
• What is Barium sulfate used for?

  'Barium Meal'-used to diagnose stomach problems-it coats the tissue then shows up on x-ray.It's not harmful as it's insoluable so won't dissolve in the body.
• What is Magnesium sulfate used for?

  'Epsom salt'-a mineral used to replace magnesium in the body to increase water in the intestines.

  Magnesium in the extraction of Titanium:

  TiCl4(g) + 2Mg(l)  Ti(s) + 2MgCl2(l)
• What is CaO used for and equation?

  As a flue gas removing SO2

  CaO(s)+SO2(g)+2H20(l)→CaSO3(s)+2H20(l)+CO2(g)
• Group 2 reaction with waterequation

  metal (s)+2H20(l)→metal hydroxide(aq)+H2(g)
• What is the exception to the group 2 reactions with water?

  Mg-reacts very slowly with cold water,so instead reacts with hot steam.

  Mg(s)+H20(g)→MgO(s)+H2(g)
• Key properties


  -Solid at room temp

  -Metallic bonding
• General trend of IE

  -Ionisation energy decreases as you go down Group 2:

  -atoms get bigger

  -more shielding

  -therefore weaker attraction from nucleus to electrons in outer shell
• General trend of mp

  -MP:Decreases.Increased distance between delocalised electrons and nucleus(metal ions get bigger)This means the attraction between the delocalised electron and nucleus gets weaker,therefore metallic bond gets weaker.
• Atomic radius,shielding,nuclear charge trends

  -Atomic radius+ionic radius decrease down group 2 -more electron shells so bigger atoms

  -Shielding increases down group-1 extra fully-occupied electron shell added before outer shell.This extra shell of electrons shield outer electrons more.

  -Nuclear charge increases down group-more protons.
• Extraction


  process of separating the metal from its ore.
• stages titanium is extracted by its ore


  1)Titanium dioxide heated with carbon and chlorine,to form titanium chloride TiO2+2Cl2+2C→TiCl4+2CO

  2)Then,the titanium is reduced by magnesium which forms magnesium chloride →TiCl4 +2Mg→Ti +2MgCl2
• Why isn't carbon used to extract titanium?

  Heating titanium dioxide with carbon produces a carbide which is too brittle to be useful as an engineering material.

  TiO2(s)+C(s)→TiC(s) +O2(g)
• use of calcium-calcium compound to prevent acid rain

  -Burning fossil fuels form so2,which causes acid rain

  -Two alternatives to spray over so2 instead:quicklime and limestone.
• quicklime to prevent acid rain

  -quicklime is mixed with water to form slurry(mixture) and is sprayed over so2 to form calcium sulfite solid

  CaO(s)+SO2(g)→CaSO3(s)
• limestone to prevent acid rain-


  -same process as quicklime but with calcium carbonate

  CaCO3(s)+SO2(g)→CaSO3(s)+CO2(g)
• group 2 reactivity with water

  -Reactivity increases down group-more vigorous.This is becase sum of sum of 2nd IE decreases therefore the activation energy to form s metal hydroxide decreases.
• the reactions with water:

  -beryllium doesn't react with water at room temp

  -magnesium with steam(alternative)

  Mg(s)+H2O(l)→MgO(s) +H2(g)

  -magnesium with cold water:reacts very slowly

  Mg(s) +2H2O(g)→Mg(OH)2(s)+H2(g)
• solubility rules

  -hydroxides solubility increase down the group

  -sulfates solubility decrease down the group

  -Barium sulfate insoluble,

  -caclium hydroxide and calcium sulfate sparingly soluble.
• compounds to remember

  slaked slime and lime water-Ca(OH)2
• uses of Mg(OH)2

  treats indigestion by neutralising stomach acid.
• uses of Ca(OH)2 (slaked lime)

  used to neutralise acidic soils and to encourage growth of plants.
• use of BaSO4 (barium meal)

  -used to diagnose stomach problems.It coats the tissue then shows up on x-rays-this is safe because barium sulfate is insoluable and won't dissolve in the body to cause harm.
• use of MgSO4

  epsom salt-a mineral used to replace magnesium in the body to increase water in the intestines.
• oxidation of group 2 metals

  -they lose electrons when reacting e.g. metal - metal 2+ charge +2e-

  reaction is :metal → metal 2+ (charge) +2e-